/* 
    类型别名也就是自定义类型
 */
let d1: (number | string)[] = [1, 2, "a", "b"];
let d2: (number | string)[] = [1, 2, "a", "b"];
let d3: (number | string)[] = [1, 2, "a", "b"];
let d4: (number | string)[] = [1, 2, "a", "b"];

// 类型别名的使用
type myArray = (number | string)[]
let a1: myArray = [1, 2, "a", "b"];
let a2: myArray = [1, 2, "a", "b"];
let a3: myArray = [1, 2, "a", "b"];
let a4: myArray = [1, 2, "a", "b"];